Non-destruction evaluation (NDE) is becoming an increasingly valuable tool in many aspects of industry, research, and technology development. One promising method of NDE is the use of ultrasound to investigate materials and structures with no adverse effect on the material or structure.
The ways in which ultrasound is sent through and into a material, and then its echos received, are many and well known. Presently, the most significant problems involve the ability to understand the content of the ultrasonic echos received back, and to recognize what type of ultrasonic inspection is needed for optimal results.
Recently, significant advances have been made in the mathematical processes which are used to evaluate the received ultrasound. In particular, inverse elastic wave scattering theories have been improved so that they can be applied to different ultrasonic frequency ranges, and different types of material evaluations. For example, using these theories, flaws in a material can be quantitatively approximated as to size, shape, and orientation.
Although the mathematical theories have been advanced to cover wide frequency ultrasound information, as of yet, there has not been a satisfactory means or method for actually generating sufficiently broadband, ultrasonic pulses for transmitting and receiving in ultrasonic NDE inspection to take full advantage of the advances. The state of the art commercial ultrasonic instrumentation and transducers have bandwidths too narrow to adequately employ the inverse scattering theories for a range of different material properties, and most significantly, for a range of flaw sizes.
Without adequate frequency bandwidth, estimates and approximations for ultrasonic NDE evaluation and inspection will have margins of error which are too great for reliability. Furthermore, it disallows application of the ultrasonic inspection to analyze flaws or material properties of various sizes.
It has been determined that one method to improve transducer bandwidth is to utilize unipolar pulses. In one attempt to utilize unipolar pulses, a first transducer, being connected to a low impedance electronic pulser, transmitted an ultrasonic signal to the material being evaluated. A second transducer connected to a high impedance amplifier received the reflection or echo of these ultrasonic pulses. The system tried to emulate unipolar pulses to broaden bandwidth, by utilizing one transducer to "pitch" the ultrasound, and another transducer to "catch" the ultrasound. The transducers of this system are set to be in a pitch-catch mode.
However, NDE ultrasound evaluation most times requires the use of one transducer only for both transmitting and receiving. This is called utilizing the transducer in the "pulse-echo mode". No adequate means or method for generating the desired broadband, unipolar pulses using a conventional planar transducer has been developed.
It is therefore a primary object of the present invention to produce a means and method for transmitting and receiving broadband, unipolar ultrasonic pulses for non-destructive evaluation and inspection which improves over or solves the problems and deficiencies in the art.
Another object of the present invention is to provide a means and method as above described which improves the frequency bandwidth of ultrasound for NDE inspection.
A further object of the present invention is to provide a means and method as above described which presents a low impedance path between the pulse transmitter and the transducer, and presents a high impedance electrical pathway between the transducer and the output.
Another object of the present invention is to provide a means and method as above described which produces broadband, unipolar ultrasonic pulses utilizing a single transducer as both a transmitter and receiver.
Another object of the present invention is to provide a means and method as above described, which improves the reliability and accuracy of evaluation of estimates of ultrasonic non-destructive evaluation.
A further object of the present invention is to provide a means and method as above described which provides accurate and reliable results for a variety of material flaw sizes and material properties.
A further object of the present invention is to provide a means and method as above described which is accurate, reliable, and easily adaptable to a variety of NDE systems.
Another object of the present invention is to provide a means and method as above described which is economical and versatile.
Another object is to provide a means and method as above described which comprises a coupling network for coupling a transmitter, transducer and receiver together to provide a unipolar ultrasonic pulse with low impedance coupling from transmitter to transducer, and high impedance coupling for transducer to receiver. This coupling can be provided as a separate transmit/receive switch or incorporated into the transmitter and receiver to achieve the same results.
These and other objects, features, and advantages of the present invention will become more apparent with reference to the accompanying specification and claims.